Five people are reported slain, as security forces face off with defiant protesters in Aleppo, Homs, Hama and Dair Alzour among other cities.

Reporting from Beirut — In widespread, unyielding defiance of President Bashar Assad's authoritarian regime, protests erupted across Syria after midday prayers Friday, drawing hundreds of thousands, with especially large demonstrations in Hama and Dair Alzour, according to witnesses, activists and video clips.

Protesters, at times faced with gunfire, tear gas or beatings, stridently demanded the end of a government that has responded with violence to their movement for democracy, sending refugees across borders and sharpening political and sectarian animosities throughout the Middle East.

At least five people were killed, according to reports, as security forces confronted the demonstrators. Two of the dead were in the country's second largest city, Aleppo, a commercial and cultural center whose relative quiet has long been seen as a pillar of middle-class support for Assad, activists said.

Security forces fired on demonstrators, especially in Homs, Syria's third-largest city, and nearby Aleppo, where plainclothes and uniformed security forces beat worshipers at a mosque in an attack captured on amateur videos.

"Security forces stormed the Amena Mosque and began beating people recklessly and arrested a lot of people," said Mahmoud, 34, an accountant in Aleppo who declined to give his last name. "I saw one person on the ground being beaten by more than 10 people. I think he lost his life."

Though protests broke out in the suburbs of Damascus, activists said the capital was relatively quiet. One person in the Damascus suburb of Barzeh described a huge security presence, with forces closing off roads in and out of the country's largest metropolitan area.

Hama and Aleppo, both potentially volatile religious mosaics of Sunni Muslims, Shiite denominations and Christians, were epicenters of a 1982 rebellion against the Assad family's decades-long rule.

Activists estimate more than 2,000 people have been killed so far in the four-month-old popular uprising. The latest uptick in violence comes about a week before the start of the Islamic holy month of Ramadan, when observant Muslims fast from dawn to dusk and gather daily for additional prayers.

Syrian security forces seem to be gearing up for a confrontation, especially in Homs, where the apparent abduction and killing of several members of Assad's minority Alawite Muslim community last week led to an all-out military assault, with tank or artillery shells being fired at Sunni mosque minarets and residential districts, according to videos posted to the Internet.

Dozens of people have been killed over the last week activists and observers say, in what they describe as a cynical attempt by Assad to recast the antigovernment protests as a sectarian war between majority Sunnis and Alawites, a small Shiite Muslim offshoot.

"That is what the regime wants everyone to believe so they become afraid," said a Western diplomat in Damascus, who spoke on condition of anonymity. "And that is the challenge for the opposition — they have to opt out of fearful propaganda and show that they are unified."

The loose collection of protest leaders, who have given each Friday of protests a theme, called the latest civil disobedience the day of "The Descendants of Khalid," a 7th-century follower of the prophet Muhammad. As a military commander, he unified the Arabian Peninsula and was buried in Homs. The symbolism was aimed at fusing the country's nationalist and religious sentiments to the aspirations of the protest movement, as well as emphasizing the long-espoused theme of national unity in the face of potential sectarian strife.

"One flag, one people, one country," said a banner in Dair Alzour, once a bastion of regime support near the Iraqi border.

A man reached at home in Homs via satellite phone said he could hear sporadic gunfire. He asked not to be named for fear of retribution. Authorities have begun aggressively targeting activists who provide information to independent journalists.

Another witness west of Homs, who gave his name as Hassan, said the army was deploying along the border with Lebanon and that there was heavy gunfire in Homs.

"Large squads of mukhabarat [Syrian intelligence] and shabiha [pro-government militiamen] are roaming the streets inside the city," he said. "The Syrian army is deploying on the border. There are tanks and army members on some rooftops in villages near the border. They're worried about demonstrations and want to make sure that those injured in protests are not brought over the Lebanese border."